Fluid assisted hole punching



United States Patent Inventor: Francis Joseph Fuchs, Jr.

Princeton Junction, New Jersey Application No.: 768,419

Filed: Oct. 17, 1968 Patented: Aug. 4, 1970 Assignee: Western Electric Company Incorporated New York, New York a Corp. of New York FLUID ASSISTED HOLE PUNCI-IING 21 Claims, Drawing Figs.

US. Cl. 83/22, 83/14, 83/53, 83/55, 83/685 Int. Cl. B26f l/26, I B26f l/l4 Field ofSearch 83/l4, 22,

[56] References Cited I UNITED STATES PATENTS l,478,44l l2/l923 Leveque 83/53X 1,510,008 9/l924 Lumb Primary Examiner- James M. Meister ,Att0rneyH. J. Winegar, R. P. Miller, and W. M. Kain ABSTRACT: A hole is punched in or through a blank of material by subjecting the blank to pressurized fluid in the area to be punched, and by advancing a punch through the pressurized fluid and into the blank ofmaterial in the area subjected to pressurized fluid. ln through hole punching, pressurized fluid assists the punch in separating a slug of material from the blank by shear propagation. Single and multiple hole I punching techniques, according to the present invention,

which are accomplished in a single operation, are also taught.

Patented Aug. 4, 1970 3,522,749

FIG/

PRIOR) ART INVENTOR F. .1 FUCHS, use.

By MAR/V 8 JA/VGARA T H/S ATTORNEYS US. PATENT 3,522,749 I FLUID ASSISTED HOLE PUNCI-IING BACKGROUND OF THE INVENTION 1. Field of the Invention The invention is concerned with punching holes in or through materials, and is particularly useful in the punching of dimensionally uniform holes and the punching of deep holes," i.e., holes wherein the ratio of hole depth to hole diameter is relatively large. The invention is also concerned with the multiple punching of such holes in a single operation. For convenience of presentation, it will be understood that in this specification and the appended claims, that unless otherwise specifically described, the term hole' is used generically to describe and mean both a through hole and a hole formed only partially through material.

.2. Description of the Prior Art Generally, in the prior art hole punching techniques, a solid punch of hard material is driven or forced through a less hard material to mechanically shear or fracture out a slug of material. The holes formed by such prior art techniques are typically ragged and of non-uniform dimension, i.e. the diameter of the punched hole is not constant throughout its depth, particularly where the holes are deep holes. Accordingly, limitation of depth and non-uniformity of holes formed by punching have been persistent problems in the prior art and ones that have limited the usefulness and applicability of the prior art hole punching techniques.

Additional problems present in the prior art hole punching technique described generally above, and which problems also impose undesirable limitations and restrictions on the use of punching as a technique of hole forming, are that, as the punch is driven or forced into the material, large frictional forces are developed between the punch and the material, and some of the displaced material pinches tightly against the ad- ,vancing punch. These frictional forces, and the pinching effect, can become so great,a s to stop the inward advance of the punch and to cause breaking of the punch itself. These two factors, generally, are the significant factors in limiting the depth to which a hole can be punched by the typical prior art hole punching technique.

SUMMARY OF THE INVENTION In the hole punching technique of the present invention, pressurized fluid enters between the advancing punch and the surrounding wall of the material to be punched to (i) reduce or greatly eliminate friction between the punch and the material; (ii) the pinching effect of displaced material; and (iii) to create stress concentrations in the material which tend to propagate cracks formed in the material by the penetrating punch. These results enable the punching of deeper holes and the punching of holes of greater uniformity of diameter than have been heretofore obtainable.

BRIEF DESCRIPTION OF THE DRAWINGS The disadvantages inherent in the prior art punching techniques, and the manner in which the method and apparatus of the present invention overcome these disadvantages and provide improved results, will be more completely understood by reference to the following detailed description when considered in the light ofthe attached drawing, wherein:

FIGS. 1(a), (b), and (c) are schematic representations of three stages of the punching cycle of a typical prior art punching technique;

FIGS. 2(a), (b), (c) and (d) are schematic representations of three stages of the punching cycle of a hole-punching technique in accordance with the present invention;

FIG. 3 is a cross-sectional, elevational view of a novel apparatus for practicing the method of the present invention;

FIG. 4 is a cross-sectional, elevational view ofone embodiment of an apparatus according to the present invention for punching multiple holes through a blank in a single manufacturing operation;

FIG. 5 is a cross-sectional, elevational view of a second embodiment of an apparatus according to the present invention for punching multiple holes through a blank in a single manufacturing operation; and

FIG. 6 is a cross-sectional, elevational view of a third embodiment of an apparatus according to the present invention for punching multiple holes through a blank in a single manufacturing operation.

DETAILED DESCRIPTION The advantages of the method and apparatus of the present invention, and how they affect a significant advance in the art of hole punching, can be more readily appreciated by first considering, in detail, a typical prior art hole-punching technique and the problems presented thereby.

Referring to FIG. 1(a), there is shown, schematically, a typical prior art set-up for punching a hole through a blank of material 10. The set-up includes a cylindrical punching tool 12 which is mounted for advancement and retraction through the blank plate 10 by a suitable motive device (not shown). The blank is positioned upon a die plate 14 which has a die opening 16 formed therein. The opening 16 is coaxial with and slightly larger than punching tool 12 so as to accommodate the advancement and retraction of the tool as required, while the die 16 is of adequate size to support the blank for punching.

Advancement of the punching tool into the blank, as shown in FIG. l(b), causes some material under the punching tool to be compressed, and other material to be displaced from under the punching tool upwardly around the edges thereof, so as to exert a pinching" force against the outer surface of the punching tool. The flow of the material and the pinching" forces are represented schematically by arrows 17. The forces indicated by the arrows 17 place, or tend to place, the local blank material in net compressional stress which closes or tends to close cracks formed in the material by the advancing punch 12, thus opposing the formation ofa hole. In addition to the pinching" effect, there is surface-to-surface contact between the blank material and that portion of the outer surface 15 of the punching tool which extends into the blank. The surface-to-surfaee contact causes frictional forces which resist movement of the punching tool, either into or out of the blank. The combined forces generated by the pinching" effect and the surface-to-surface contact, exert a significant load on the motive apparatus for the punching tool and on the tool itself. Often this load has been the limiting factor in determining the thickness of material through which a hole can be punched since the loads generated during deep-hole punching can easily exceed the axial strength of a punching tool, thus causing the tool to fail.

Another disadvantage of prior art punching techniques has been the lack of dimensional uniformity of the punched hole. Thus, in FIG. l(c), it can be seen that the hole punched by tool 12 through blank 10 includes a relatively uniform upper portion 18 and a ragged, non-uniform lower portion I9. This non-uniformity is caused by the manner in which the blank material fails during punching to form a hole and a punched out slug.

The slug, designated generally by the reference numeral 20 in FIG. l(c). includes a relatively uniform upper portion 22, a ragged tapered portion 24, and a relatively large diameter, smoothly finished portion 26. Additionally, the thickness T, of the slug 20 is significantly smaller than the original thickness T of blank 10. Each of these physical characteristics is caused by the manner in which the blank fails in response to the advancement of punching tool 12. More specifically, the decrease in thickness is caused by the compression of the blank material under the punching tool during its initial advance, i.e. prior to final shearing or separation of the slug from the blank. Thus, the initial advance of the tool causes compression of the blank material in the area under the punch and, coincidental with the compression, a shearing of the blank material to form the upper portion 18 of the hole and the relatively uniform portion 22 of the slug. Continued advance of tool 12 into the blank causes further compression of the blank material, and therewith, a build-up of static energy within the blank material under the tool. When the forces exerted by the advancing tool andby the effect of the static energy increase sufficiently, the remaining material under the punch separates from the blank suddenly. Such separation which can be described as a sudden shear or cleavage, occurs at an angle a (FIG. l(c)) with respect to the axis of movement of the punch, and which angularity causes the lower portion of the hole 19 to be non-uniform and the ragged portion 24 of the slug 20 to be tapered.

In addition to causing the formation of the tapered, ragged portion 24 on slug 20, the angularity of the line along which the shear occurs also causes, indirectly, the formation on the lower portion of the slug of the relatively large diameter, smoothly-finished portion 26. Referring to FIG. l(c), it can be seen that the angle (1,, at which the sudden shearing occurs, is sufficiently large to place the line of shear outside the opening of the hole 16 in die plate 14. This, in the absence of more, would preclude discharge of the slug 20 through die opening 16. The force of the advancing punching tool, however, is

such as to deform the sheared material so as to force the slug through opening 16. The forcing of the sheared material through die opening 16 comprises, substantially, an extrusion of the outer portion of the slug 20 so as to form the smoothlyfinished portion 26 of substantially the same diameter as the die opening 16.

ln the light of the above discussion, the problems ofthe conventional prior art techniques, such as that shown, are quite apparent, viz., the hole formed is ragged and non-uniform, and the motive force for driving punching tool 12 must be sufficient to overcome the aforementioned pinching effect," to overcome the aforementioned tool-wall frictional force, to extrude the slug through the hole 16 in the plate 14, and to accomplish the actual punching ofa hole in the blank 10 without causing failure in the punching tool as a result of axial overstress.

The method of the present invention, as shown schematically in FIGS. 2(a), (b) and (c), avoids completely, or substantially minimizes the above-noted problems. Considering initially FIG. 2(a), there is shown a blank of material 30 positioned on a die plate 32 over a die opening 34 A punching tool 36 is reciprocably mounted over blank 30 in axial alignment with die opening 34. A body of pressurized fluid 38 suitably contained within a pressure vessel (partially shown), is in contact with the upper surface 39 ofthe blank 30 in the area to be punched, and also in contact with the peripheral surface of the punching tool 36. As will be discussed in greater detail with respect to a description of an apparatus for practicing the method of this invention, suitable means (not shown in FIG. 2) are provided for pressurizing the fluid 38.

Referring to FIG. 2(b), it can be seen that the surface 39 of blank 30 in the area to be punched, is subjected to the pressurized fluid 38.

Thus, with the fluid 38 in vessel 37 suitably pressurized, and referring again to FIG. 2(b), it can be seen that the advance of punching tool 36 into blank 30 is accompanied by a flow, or intrusion of the highly pressurized fluid 38 between the tool 36 and the wall 40 of the hole being formed. The presence of pressurized fluid between the tool 36 and wall 40 serves three purposes: first, it expands the hole walls away from the tool,

thereby eliminating surface-to-surface tool-blank friction; secondly, it exerts radially ourwardly directed stress against the upper portion of the material defining the hole being punched which overcomes the effect of pinching as' discussed above; and finally, the fluid exerts both axially downwardly directed and radially outwardly directed stresses (as indicated by arrows 41 in FIG. 2(c)), the vectorial resultant of which stresses acts as stress concentrations acting downwardly at an angle generally along the irregular line 42. The stress concentrations indicated by arrows 41 place, or tend to place, the local blank material in net tensional stress which tends to propagate cracks (indicated by the irregular line 42) formed in the material by the downwardly directed axial stress provided by the mechanical punching action of the tool 36.

Continued advance of the punching tool 36 results ultimately in the separation of a slug, designated generally by the reference numeral 44 in FIG. 2(c), from blank 30. Although the general nature of the separation of the slug 44 from the blank 30 is similar for both the prior art (FIG. I) and the present invention (FIG. 2), the hole which is formed by the present invention has been found to be much more uniform. The slug 44 formed by the present invention includes a relatively uniform upper portion 45, and a ragged, slightly tapered portion 46, the tapered portion 46 being tapered at an angle a with respect to the vertical. The thickness T of slug 44, while less than that T of blank 30, has been found to be greater than that T,, FIG. l(c), of a slug 20 formed by the prior art punching technique from a comparable plate. Similarly, the angle a, of the surface'along which final separation of a slug 44 from the blank plate 30 occurs, has been found to be much more acute in the practice of the present invention, than the angle a of FIG. l(c), experienced in the prior art punching. The more acute angle a contributes to the uniformity of the punched hole, as it has been found that, in some instances, the reduction in angularity has been such as to maintain the maximum diameter of the slug 44 is smaller than the diameter of opening 34 in die plate 32, thus substantially eliminating any extrusion of the slug through the die plate, and thereby further facilitating the hole punching operation. Significantly, it appears that the acuteness of angle a will allow punching to be used as a technique for forming holes in much thicker material than has heretofore been possible. Additionally, the surrounding of the punching tool pressurized fluid provides radial support for the tool so as to reduce the likelihood of tool failure from overload during punching.

Thus, it will be appreciated by those skilled in the art that the present invention by eliminating, or substantially reducing, the punching effect, the friction between the punching tool and the blank of material, and by placing the local material in net tensional stress to assist in propagating material cracks created by the advancing punch tool, provides for the punching of holes of greater dimensional uniformity, and the punching of deeper holes, than provided by the prior art hole punching techniques.

lt will be further understood by those skilled in the art, that the pressure level to which the fluid 38 must be pressurized to provide the above-stated results and advantages, will vary in accordance with the yield strength of the material to be punched, the diameter of the hole to be punched, the thickness of the material to be punched, and the motive force behind the punching tool. Thus, for each set of conditions, there will exist an optimum pressure range for achieving the most efficient punching of the hole. Such optimum pressure range will vary from material to material but is reasonably well definable for a given set of aforementioned conditions and which can be determined readily by experimentation and the development of empirical data. For example, and for a given set of conditions mentioned above, should the fluid pressure level employed be too low, punching will be accomplished, at least primarily, solely by the punching tool as in the prior art and the slug removed will be substantially of the character of the slug 20 of FIG. l(c). Conversely, should the fluid pressure level employed be too high, the level could possibly be so high as to cause the pressurized fluid itself to unwantedly deform the material being punched, or prematurely rupture the material ahead of the punching tool; both conditions being readily observable. The optimum pressure range, however, will be that fluid pressure range extending between the aforedescribed too high and too low pressure levels, which will remove slugs substantially of the character of the slug 44 of FIG. 2 a

In the practice of the present invention (as shown schematically in FIG. 2) to punch a hole in a 1/4 inch thick brass plate,

wherein the punching tool was 0.10 inch in diameter and the die opening was 0.125 inch in diameter, a four sample average provided a punched hole having an upper or entrance diameter of 0.1010 inch and a lower or exit diameter of 0.1246 inch. The optimum pressure range was found to be from approximately 20,000 (11 to 150,000 111, with a pressure level of approximately 50,000 111 highly desirable results.

The method of the present invention, therefore, provides for the efficient, accurate punching of dimensionally uniform holes, and the punching of deep holes, in and through material blanks. The simplicity of this method lends itself to practice by relatively uncomplicated apparatus, such as punching apparatus designated generally by the reference numeral 50 in MG. 3.

Referring to F113. 3 in more detail, apparatus 50 includes a pressure vessel 52 having a first axial bore 50 extending longitudinally axially into one end thereof, and a second bore 56 extending longitudinally axially into the other end thereof to communicate with bore 5 1.

A die plate 60 is securely mounted above vessel 52 (by means not shown) and is provided with an opening 62 therethrough, which opening is coaxial with bores 54, 56 and sufficiently large to accommodate the advancement and retraction of a punching tool while at the same time adequately supporting the blank for punching. In operation, as will be discussed in greater detail, a blank of plate material 65 is secured between vessel 52 and die plate 60. Blank 65 cooperates with a seal 66 mounted in an annular aperture 67 formed in the outer end of bore 56, to establish a fluid-tight seal between vessel 52 and blank 65.

Slidably mounted within bore 51 is a piston 70 having a longitudinally axially extending bore 71 for slidably accommodating a punching tool 72 therethrough. Punching tool 72 is secured to a suitable motive means (not shown) and extends therefrom through bores 71, 54 and 56. The major diameter of tool 72 is slightly smaller than that ofbore 56 so as to allow the free and unrestricted passage of a pressure transmitting medium 75 therearound in bore 56, and to allow the medium to be in 1 contact with the upper surface of blank 65. A reduced diameter portion 74 is formed on the tool 72 at its die adjacent end, which portion 74 defines the punching or blank piercing portion of the tool.

Piston 70 is slidably received within bore 5 1 and the interface therebetween is sealed against fluid leakage by a suitable high pressure seal 77 mounted in a threaded annular channel 78 in the upper end of bore 51. Seal 77 is retained in place by a suitable retaining ring 79 which is threadedly secured in annular channel 78. Similarly, punching tool 72 is slidably received through bore 71 in piston 70, and fluid leakage is precluded around punching tool 72 through bore 71 by the provision of a suitable high pressure seal 01 mounted in a threaded annular channel 02 formed at the upper end of bore 71. Seal 81 is maintained in position by a retaining ring 03 which is threadedly secured within channel 02. Thus, as can be clearly seen from 1 18. 3, punching tool 72, piston 70, bores 54 and 56 and blank 65 cooperate to define a fluid-tight chamber 84 for receiving the fluid medium 75.

ln practicing the method of the present invention with the apparatus of FIG. 3, bores 54 and 56 are filled with a pressure transmitting medium such as fluid 75, and a blank 65 of plate material is positioned between vessel 52 and die plate 60; and die plate 60 is rigidly secured in place by suitable means (not shown). ln this position, seal 66 is tightly engaged with the lower surface of blank plate 65 to define a fluid-tight seal therewith. Thereafter, tool 72 is advanced into light contacting engagement with blank 65, and piston 70 is then advanced into bore 54 by a suitable motive means such as a ram (not shown).

The advancement of piston 70 causes an increase in the pressure offluid 75 within bore 54, which pressure increase is transmitted within chamber 76 and around punching tool 72 in bore 56 to blank 65. As discussed above, the exertion of fluid pressure on blank 65 in the area to be punched facilitates punching in accordance with the teaching of the present in vention as stated above. The advancement of piston is continued within bore 54 until the pressure in fluid is at a level which has been predetermined (as taught above) to be within the optimum pressure range for the particular blank material, and thereafter the piston 70 is advanced or retracted, as required, to maintain pressure in the vessel at the desired level.

Once the proper fluid pressure has been achieved, punching tool 72 is advanced further so as to penetrate and ultimately punch out a slug of blank material from plate 65 and form the desired hole therein as discussed above. The separation of the slug from the blank allows fluid 75 to escape through hole 62 thus relieving the fluid pressure within vessel 52. Thereafter, vessel 52 and die plate 60 are separated and the punched plate 65 is removed.

ln addition to overcoming the problems noted above with respect to difficulties experienced in attempting to punch relatively deep holes in blank plates by prior art methods, the present invention facilitates the punching of multiple holes in a blank plate by a single manufacturing operation.

Referring to MG. 4, a multiple hole punching apparatus is shown and designated generally by the reference numeral 100. Apparatus comprises a block 102 having two longitudinally axially parallel, multi-bore channels designated generally by the reference numerals 103, 104, extending therethrough. Channel 103 includes a first bore 106 extending into block 102, from the lower surface 107 thereof, a second bore 109, coaxial with first bore 106, extending into block 102 from the upper surface 110 thereof, and a third bore 112 coaxial with and extending between first and second bores 106, 109. Third bore 112 is larger in diameter than second bore 109, but smaller in diameter than first bore 106. Similarly, channel 104 includes a first bore 115 extending into block 102 from the lower surface 107 thereof, a second bore 117 coaxial with first bore 115 extending into block 102 from the upper surface 110 thereof, and a third bore 119 coaxial with and extending between first and second bores 115 and 117. Third bore 119 is larger in diameter than second bore 117, but smaller in diameter than first fore 115.

The first bores 106, 115 of channels 103, 104 respectively are closed by plugs (raised annular portions) 121, 122 which are formed on an end plate 123 which is mounted flush against the lower surface 107 of block 102 and secured thereto such as by bolts 125. Plugs 121, 122 are provided with through bores 127, 125 which are coaxial with channels 103, 104 respectively and accommodate therethrough the reciprocable passage of a pair ofpunching tools designated generally by the reference numerals 130, 131.

Punching tool comprises amain shaft 133 having a diameter substantially equal to the diameter of through bore 127, and slightly less than the diameter of third bore 112. Formed on the upper end of main shaft 133 is an axially extending reduced diameter portion 134- which defines the abtual punching portion of the punching tool 130. The lower end of tool 130 is provided with an enlarged diameter portion 136 which is secured to a ram 131! so as to power punching tool 130, as will be discussed.

Similarly to punching tool 130, punching tool 131 comprises a main shaft 1410 having a diameter substantially equal to the diameter of through bore 120 and slightly less than the diameter of third bore 119 in channel 104. Formed on the upper end of main shaft 140 is an axially extending reduced diameter portion 1412 which defines the actual punching portion of the punching tool 131. The lower end of tool 131 is provided with an enlarged diameter portion 1 13 which is rigidly secured to ram 1311.

It is to be noted that the diameters of main shafts 133, 1 10 of punching tools 130, 131 are slightly smaller than the diameters of third bores 112, 119 of channels 103 and 104 respectively. Similarly, the reduced diameter portions 134, 142 of punching tools 130, 131 are slightly smaller in diameter than the diameters of second bores 109, 117 of channels 103, 104.

The purpose of the disparity in diameters of the respective portions of the punching tools and the bores within which they reciprocate is to insure uninhibited fluid communication around the punching tools 130, 131 so as to provide radial fluid support to the punching tools as discussed above, and to define a fluid contact area, on the lower surface of blank 150 in the areas to be punched.

The upper surface 110 of block 102 defines a bed upon which a blank plate such as blank 150 is positioned prior to having holes punched therein by punching tools 130, 131. The blank 150 is held in position by a die plate 154 which is securely mounted above block 102 by suitable means (not shown). A pair of frusto-conical openings 155, 156 are formed in die plate 154, coaxial with channels 103 and 104, respectively. The blank-adjacent ends of openings 155 and 156 are coaxial with and slightly larger in diameter than the reduced diameter portions 134 and 142 of punching tools 130 and 131, respectively, so as to accommodate the advancement and retraction of the tools as required, while at the same time adequately supporting the blank for punching.

A can be seen from FIG. 4, blank 150, channel 103 and plug 121 cooperate to define a fluid tight chamber 159 around punching tool 130. Similarly, blank 150, channel 104 and plug 122 cooperate to define a fluid tight chamber 160 around punching tool 140. Leakage from chambers 159 and 160 around plugs 121, 122 is prevented by seals 162, 163 mounted in channels in the outer and inner surfaces of plug 121, and seals 165, 166 mounted in channels in the outer and inner surfaces of plug 122. In a like manner, leakage from chambers 159 and 160 between the upper surface 110 of block 102 and blank 150 is prevented by the provision of seals 168, 169 mounted in annular channels formed concentrically around second bores 109, 117 respectively.

Fluid chambers 159 and 160 are in communication through a passage 171 extending therebetween. Fluid is supplied to both chambers from a high pressure fluid supply line 173 through a passage 174 which extends from the outer surface of block 102 into chamber 159 the fluid thereafter passing from chamber 159 through passage 171 into chamber 160.

The operation of the apparatus of FIG. 4 for punching holes in blank 150 is initiated by filling chambers 159 and 160 with fluid from high pressure fluid line 173. Thereafter, blank 150 is positioned on the upper surface 110 of block 102 so that the centers of the areas to be punched coincide with the axes of channels 103 and 104. Die plate 154 is then positioned on blank 150 and secured (by means not shown) so as to rigidly maintain blank 150 in position for punching and to cause engagement of the lower surface of blank 150 with seals 168, 169 to seal chambers 159, 160 against fluid leakage therefrom.

At this stage in the operation, ram 138 is advanced, i.e. displaced upwardly as seen in FIG. 4, until the reduced diameter portions 134, 142 ofpunching tools 130, 131, come into initial engagement with the surface of blank 150. The pressure in chambers 159 and 160 is then increased, by increasing the pressure of fluid in high pressure fluid supply line 173, until the pressure is sufficiently great to facilitate punching in accordance with the method of the present invention. Thereafter, the advancement of ram 138 is continued until the reduced diameter portions 134, 142 of punching tools 130, 131 respectively, completely penetrate blank 150. Upon the completion of penetration, the pressure in chambers 159 and 160 is relieved, ram 138 is retracted and therewith punching tools 130 and 131, die plate 154 is removed and the finished punched blank 150 is removed from the apparatus. Once the punched blank is removed, the apparatus is ready to receive a new blank for repeating the operation.

Referring now to FIG. 5, there is shown an apparatus for punching multiple holes in a blank, designated generally by the numeral 200, which is substantially the same as the apparatus shown in FIG. 4 with the exception of the structure for and manner of advancing the punching tools.

Broadly, apparatus 200 includes a block 202 having two channels 203, 204 which are of substantially the same configuration as the channels 103, 104 of the apparatus of FIG. 4. Thus, channel 203 comprises first, second and third coaxial bores 206, 209, 212 respectively, and channel 204 comprises first, second and third coaxial bores 215, 217, 219 respectively. The lower ends of first bores 206, 215, in channels 203, 204 are threaded for receiving, in a fluid-tight manner, threaded plugs 221, 222 therein. Each plug 221, 222 is provided with an axial passage 224, 225 therethrough extending from its outer surface to counter-bores 226, 227 formed on the inner surface thereof. As will be discussed in detail below, passages 224, 225 are connected to high pressure fluid lines 227, 228, respectively which are connected to a source ofhigh pressure fluid (not shown).

Channel 203 contains a reciprocable punching tool designated generally by the reference numeral 230. Punching tool 230 comprises a main shaft 233 which has an axially extending reduced diameter portion 234 on its upper end, which reduced diameter portion is coaxial with channel 203 and of slightly smaller diameter than the diameter of second bore 209 1 to allow the passage of fluid therebetween. Additionally, punching tool 230 is provided with an enlarged diameter portion formed on its lower end, the diameter of which portion is substantially equal to the diameter of first bore 206, so as to define a piston 236 for reciprocation within bore 206. Passage of fluid around piston 236 is prevented by the provision of a seal 237 mounted in an annular channel formed in the peripheral surface thereof.

In like manner, channel 204 contains a reciprocable punching tool designated generally by the reference numeral 231. Punching tool 231 comprises a main shaft 240 which has an axially extending reduced diameter portion 242 on its upper end which reduced diameter portion is coaxial with channel 204 and of slightly smaller diameter than the diameter of second bore 217 to allow the passage offluid therebetween. Additionally, punching tool 231 is provided with an enlarged diameter portion formed on its lower end, the diameter of which portion being substantially equal to the diameter offirst bore 215, so as to define a piston 243 for reciprocation within bore 215. Passage of fluid around piston 243 is prevented by the provision of a seal 244 mounted in an annular channel formed in the peripheral surface thereof.

The upper surface 210 of block 202 defines a bed upon which a blank plate such as blank 250 is positioned prior to having holes punched therein by punching tools 230, 231. The blank 250 is held in position by a die plate 254 which is securely mounted above block 202 by suitable means (not shown). A pair of frusto-conical openings 255, 256 are formed in die plate 254, coaxial with channels 203-and 204 respectively. As was the case with the embodiment of FIG. 4, the blank-adjacent ends of openings 255 and 256 are coaxial with and slightly larger in diameter than the reduced diameter portions 234 and 242 of punching tools 230 and 231 respectively "so as to accommodate the advancement and retraction of the punching tools as required, while at the same time adequately supporting the blank for punching.

Punching tool 230 cooperates with channel 203, plug 221 and blank 250 to define a plurality of fluid type chambers. Thus, the upper radial surface 261 of the main shaft 233 of punching tool 230 cooperates with second bore 209 and third bore 212 of channel 203 as well as the lower surface of blank 250 to define a first fluid chamber 263 around the reduced diameter portion 234 of punching tool 230. Similarly, the inner surface of plug 221 and the lower surface of piston 236 cooperate with first bore 206 to define a second fluid chamber 265. Leakage of fluid from first fluid chamber 263 around the main shaft 233 of punching tool 230 is prevented by a seal 267 mounted in an annular channel formed in the surface of third bore 212. The space in first bore 206 above piston 236 and below seal 267 in third bore 212 is vented to the atmosphere through a passage formed in block 202.

Punching tool 231 cooperates with channel 204, plug 222, and blank 250 to define a plurality of fluid chambers. Thus the upper surface 262 of the main shaft 240 of punching tool 231 cooperates with second bore 217 and third bore 219 ofchannel 204 as well as the lower surface of blank 250 to define a first fluid chamber 264 around the reduced diameter portion 242 of punching tool 231. Similarly, the inner surface of plug 222 and the lower surface of piston 243 cooperate with first bore 215 to define a second fluid chamber 266. Leakage of fluid from first fluid chamber 264 around the main shaft 240 of punching tool 231 is prevented by a seal 269 mounted in an annular channel formed in the surface of third bore 219. The space in first bore 215 above piston 243 and below seal 269 in third bore 219 is vented to the atmosphere through a passage 270 formed in block 202.

Upper surfaces 261, 262 of the main shafts 233, 240 of punching tools 230, 231 are provided with annular channels for receiving sealing rings 281 and 282. These sealing rings are engageable with the radial shoulders 284, 285 formed at the intersection of bores 209 and 212, and of bores 217 and 219, respectively. As will be discussed further in greater detail, these seals preclude loss of pressure from chambers 263 or 264 in the event that penetration of blank 250 by punches 230,231 does not occur simultaneously.

First fluid chamber 263 in channel 203 and first fluid chamber 264 in channel 204 are in fluid communication through a passage 271 formed therebetween in block 202 which, in turn, is in communication with a high pressure fluid source line 272 through a passage 273 formed in block 202 between channels 203 and 204.

The operation of apparatus 200 for punching holes in blank 250 is initiated by filling chambers 263-266 with fluid from high pressure fluid lines 227, 228 and 272. Thereafter, blank 250 is positioned on the upper surface 210 of block 202, so

that the centers of the areas to be punched coincide with the axes ofchannels 203 and 204. Die plate 254 is then positioned on blank 250 and secured (by means not shown) so as to rigidly maintain blank 250 in position for punching and to cause engagement of the lower surface of blank 250 with seals 273, 274 which are mounted in annular passages formed in the upper surface of blank 202, concentrically around second bores 209 and 217, to seal chambers 263 and 264 against fluid leakage therefrom.

At this stage, the pressure in chambers 263-266 is increased until the reduced diameter portions 234 and 242 of punching tools 231 come into initial engagement with the lower surface of blank 250. The pressure in chambers 263-266 is then further increased until it is within the optimum pressure range described above, to thereby facilitate punching in accordance with the method of the present invention and to advance punching tools 230-231 into the blank 250 so as to cause holes to be punched therein.

It is to be noted that in the embodiment of FIG. 4 the punching tools 130 and 131 are restrained for concerted advancement by reason of their being connected to ram 138. Thus, neither punching tool 130 nor punching tool 131 can cause penetration of blank 150 in advance of penetration by the other. However, it is evident from FIG. 5 that there is no mechanical linkage which correspondingly restricts the movement of punching tools 231 and 232. It is further evident that the reduced diameter portion 234 of punching tool 230 is smaller than the reduced diameter portion 242 of punching tool 231 so as to form holes of differing sizes. As will be immediately recognized by those skilled in this art, therefore, it is likely that the penetration of blank 250 by punching tools 230, 231 will not occur simultaneously. This is caused by either or both of two things: (a) the fact that the holes to be punched are of different diameters, and (b) the fact that most blank plates, notwithstanding the care with which they are manufactured, exhibit varying degrees of resistance to punching. Obviously, when penetration of blank 250 by either of punching tools 230 or 231 occurs, the pressure seal for either chamber 263 or 264 is lost. Further, since chambers 263 and 264 are in communication through fluid passage 271, a loss of pressure in one causes a corresponding loss of pressure in the other, which loss of pressure would in the absence of more, preclude the completion of punching of the remaining holes in a high fluid pressure environment. Such loss of pressure in one chamber, which would affect the pressurization of the other chamber, is precluded in the embodiment of FIG. 5.

Assuming that the smaller hole, i.e. that to be punched by punching tool 230 is punched before the larger hole, it can be seen that the formation of the hole destroys the pressure seal of chamber 263 thereby eliminating all force of retardation against the effect of high pressure fluid acting against the piston 236 in fluid chamber 265. The punching tool, therefore, is displaced upwardly thereby causing the seal 281 in the upper end of main shaft 233 to engage the shoulder 284 to establish a fluid-tight seal therebetween. In this manner, leakage of fluid from chamber 263 through the newly formed hole around the reduced diameter portion 234 of punching tool 230 is prevented, and the pressure integrity of chamber 264 is maintained until the larger hole is formed. Similarly, if punching tool 231 penetrates blank 250 before punching tool 230, the tool 231 is displaced upwardly by the action of the pressurized fluid in chamber 266 against piston 243, seal 282 engages radial surface 285 and the pressure integrity of chamber 263 ismaintained until the smaller hole is formed.

Upon the completion of punching of both holes, the pressure in high pressure fluid lines 226, 228 and 272 is relieved thereby allowing punching tools 230, 231 to move downwardly within tools 203 and 204. Die plate 254 is removed thereafter and the finished punched blank 250 is removed from the apparatus. With the finished blank now clear, the apparatus is ready to receive a new blank for repeating the operation.

Referring now to FIG. 6, there is shown another embodiment of an apparatus in accordance with the present invention, which apparatus is designated by the reference numeral 300.

Apparatus 300 is quite similar to the apparatus of FIG. 4 in that it comprises generally a block 302 having channels 303, 304 in which punching tools 330, 331 are reciprocated by a ram 338 so as to punch suitable holes in a blank 350, which is positioned on the upper surface 310 of block 302 and retained by die plate 354.

Channel 303 in apparatus 300 comprises a first bore 306 extending into the block 302 for the major portion of its depth and a second bore 309 which is coaxial with first bore 306 and extends through the remaining portion of block 302. Similarly, channel 304 comprises a first bore 315 extending into block 302 through the major portion of its depth and a second bore 317 which is coaxial with first bore 315 and extends through the remaining depth of block 302.

Punching tool 330 comprises a main shaft portion 333 which has a diameter substantially equal to the diameter of first bore 306 and is slidably received therein. Formed coaxially on the upper end of main shaft 333 is an axially extending reduced diameter portion 334 which defines the actual punching portion of tool 330. The lower end of tool 330 is provided with an enlarged diameter portion 336 which is secured to ram 338 so as to power punching tool 330 as will be discussed.

Similarly, punching tool 331 comprises a main shaft 340 having a diameter substantially equal to the diameter of first bore 315 from being slidably received therein. A reduced diameter portion 342 is also formed on the upper end of main shaft 340 of punching tool 331, and the lower portion of main shaft 340 is provided with an enlarged diameter portion 343 which is rigidly secured to ram 338.

The reduced diameter portions 334, 342 are slightly smaller in diameter than second bores 309, 317 respectively so as to allow the relatively unrestricted passage therearound of fluid.

With blank 350 in position on the upper surface 310 with block 302 and held rigidly in place by die plate 354 so as to be in sealing engagement with seals 368 and 369 which are positioned around bores 309, 317, it can be seen that a fluid-tight chamber 363 is defined in channel 303 by the cooperation of the upper surface 361, of main shaft 333, of the lower surface of blank 350, and first and second bores 306, 309. Leakage of fluid from chamber 363 between main shaft 333 and bore 306 is precluded by the provision of a seal 367 mounted in an annular channel formed in the peripheral surface of main shaft 333 adjacent its upper end. Similarly, a fluid-tight chamber 364 in channel 304 is defined by the upper surface 362 of main shaft 340, the lower surface of blank 350 and first and second bores 315 and 317. Leakage of fluid from chamber 364 between main shaft 340 and first bore 315 is precluded by the provision ofa seal 344 in an annular channel formed in the peripheral surface of main shaft 340 adjacent its upper end.

A passage 371 communicates fluid chamber 363 with a vent passage 372 which extends through block 302 to the atmosphere. The flow of fluid from chamber 363 through passage 371 and thereafter to the atmosphere through passage 372 is controlled by a spring-loaded check valve 373 which is threadedly secured in a bore 374 in block 302. By regulating the flow of fluid from chamber 363, it can be seen that check valve 373 also determines the upper limit of pressure that can be generated in chamber 363.

Similarly, a passage 377 communicates fluid chamber 364 with a vent passage 378 which extends through block 302 to the atmosphere. The upper limit of the pressure within and the flow of fluid from chamber 364 through passage 377, and thereafter to the atmosphere through passage 378, are controlled by a spring-loaded check valve 374 which is threadedly secured in a bore 380 in block 302.

As was the case with the prior embodiments, die plate 354 is provided with a pair of frusto-conical openings 355, 356, the blank-adjacent ends of which are coaxial with and slightly larger in diameter than the diameters of the reduced diameter portions 334 and 342 of punching tools 330 and 331 respectively. In this manner, openings 355 and 356 permit the free advance and retraction of punching tools 330, 331 while providing adequate support for blank 350.

The operation of the apparatus of FIG. 6 for punching holes in blank 350 is initiated by filling chambers 363 and 364 with a liquid pressure transmitting medium. Thereafter, blank 350 is positioned in the upper surface 310 of block 302 so that the centers of the areas to be punched coincide with the axes of channels 303 and 304, die plate 354 is then positioned on blank 350 and secured (by means not shown) so as to rigidly maintain blank 350 in position for punching and to cause engagement ofthe lower surface of blank 350 with seals 368 and 369 so as to seal chambers 363 and 364 against fluid leakage therefrom around the blank.

With fluid provided and a pressure seal established in chambers 363 and 364, ram 338 is advanced i.e. displaced upwardly as seen in FIG. 6. Advancement of ram 338 causes a corresponding advance ofpunching tools 330 and 331 which, acting as pistons, pressurize the fluid in chambers 363 and 364.

Spring-loaded relief valves 373 and 379 are preset to maintain whatever pressure is desired (e.g. the optimum pressure range taught above) in chambers 363 and 364 for the particular punching operation to be accomplished. Therefore, continued advancement of punching tools 330 and 331 serves to raise the fluid pressure in chambers 363 and 364 to the desired level whereafter it is maintained and not allowed to further increase by the bleeding action of relief valves 373 and 379.

With pressure built up to the desired levels in chambers 363 and 364, the advancement of ram 338 is continued until the reduced diameter portions 334, 342 of punching tools 330, 331 respectively completely penetrate blank 350. Upon the completion of penetration, the pressure in chambers 363 and 364 is relieved, ram 338 is retracted and therewith punching tools 330 and 331, die plate 354 is removed, and the finished, punched blank 350 is removed from the apparatus. Once the punched blank is removed, the apparatus is ready to receive a fresh blank for repeating the punching operation.

It will be understood, that as mentioned in various places above, the present invention is equally useful and applicable to the punching of holes entirely through the material blank, or only part of the way through the material blank. Consequently, as stated above and repeated for emphasis and clarity, it will be understood that in the appended claims the expression punching a hole in a blank of material" is used to describe both punching a hole entirely through, or only part of the way through the blank of material.

Further, it is to be recognized that although the present invention has been disclosed in terms of apparatus for punching one or two holes in a blank plate, the present invention contemplates the punching of as many holes in a plate as are desired during a single forming operation. Further, the aforedescribed apparatus are only a few of many which can be used to practice the method of the present invention and it is to be understood that the above-described embodiments are simply illustrative of apparatus according to the present invention. Numerous other modifications, both as to the method and as to the apparatus, may be devised without departing from the spirit and scope of the invention.

lClaim:

1. Method of punching holes, which comprises:

placing one side ofa blank to be punched against a female die,

applying fluid pressure against the other side of the blank at a localized area opposite the female die, and

projecting a mechanical punch from said other side and into the blank in said localized area, to produce a hole therein, with the assistance of the pressurized fluid.

2. Method of punching holes in plate-like workpieces, which comprises:

placing one major surface of a plate against a female die so that the area of the plate to be punched is opposite the die aperture;

subjecting a portion of the other major surface to highly pressurized fluid, said portion surrounding the area to be punched and being less in area than said other major surface; and

projecting a mechanical punch through said other major surface andinto the plate to produce a hole therein, said fluid entering the hole along with the punch to assist in hole formation.

3. Method for punching a hole in a blank of material, comprising the steps of:

advancing a punching tool into said blank of material, and

concurrently, subjecting said blank of material to fluid pressurized sufficiently great to cause said fluid to enter between said punching tool and said blank material and substantially reduce any friction therebetween.

4. Method according to claim 3 wherein said fluid entering between said punching tool and said blank material is pressurized sufficiently great to produce forces placing the local blank material in net tensional stress to propagate cracks formed in said blank material by the punching action of said punching tool.

5. Method of punching a hole in a blank of material comprising the steps of:

positioning said blank of material between a die opening and a chamber-defining pressure vessel;

positioning a punching tool in said chamber;

filling the chamber of said pressure vessel with a pressure transmitting medium, said medium surrounding the periphery of said punching tool and bearing against a surface of said blank; and

advancing a punching tool into said surface ofsaid blank;

concurrently with the advancement of said punching tool, pressurizing said medium to cause said medium to exert pressure against said surface of said blank sufficiently great to cause said fluid to enter betwcensaid punching tool and said material to substantially reduce any friction therebetween, and to produce forces acting against the local blank material to place the local blank material in net tensional stress thereby propagating cracks formed in said blank material by the punching action of said punching tool.

6. Apparatus for punching a hole in a blank comprising:

a punching tool;

a vessel having a chamber formed therein for receiving a pressure transmitting medium and said punching tool means;

means for pressurizing said medium to exert pressure against a surface of said blank; and

means for advancing said punching tool into said surface of said blank.

7. The apparatus as claimed in claim 6 wherein said means for pressurizing said medium acts concurrently with the advancement of said punching tool.

8. The apparatus as claimed in claim 10 wherein said punching tool extends within said chamber so as to be surrounded by said fluid.

9. The apparatus as claimed in claim 6 wherein said means for pressurizing said medium comprises a piston mounted slidably within said chamber.

10. The apparatus as claimed in claim 6, and further includmg:

means for restricting the exposure to said pressurized fluid of said blank to substantially equal the area of said surface in which said hole is to be punched.

11. The apparatus as claimed in claim 6 wherein said means for pressuring said medium comprises a piston mounted slidably within said chamber and concentrically of said punching tool means.

12. Apparatus for punching a plurality of holes through a blank of material comprising:

a vessel having a plurality of chambers therein, each chamber for receiving fluid and for exposure to a separate surface area of said blank of material;

punching tool means mounted reciprocably in each chamber;

means for pressurizing said fluid to exert pressure against said surface areas of said blank of material; and

means for advancing each of said punching tool means through said chambers into said surface areas of said blanks.

13. Apparatus as claimed in claim 12 wherein said chambers are in fluid communication.

14. Apparatus as claimed in claim 12 wherein said punching tool means are mechanically linked for concurrent advancement and retraction.

15. Apparatus as claimed in claim 12 wherein said punching tool means are independently reciprocable within said chambers.

16. Apparatus as claimed in claim 12 and further including means mounted in said vessel for controlling the pressures of fluid received in said chambers.

17. Apparatus as claimed in claim 16 wherein each said pressure controlling means comprises a spring-loaded check valve in fluid communication with each of said chambers.

18. Apparatus as claimed in claim 12 wherein said punching tool means and said means for pressurizing said fluid in said chambers are of unitary structure and operation.

19. Apparatus as claimed in claim 12 wherein each of said punching tool means has a piston formed thereon for being acted thereagainst by said fluid for pressurizing said blank.

20. Apparatus as claimed in claim 12 wherein each of said punching tool means is provided with sealing means mounted thereon for cooperating with said vessel to preclude loss of fluid pressure from said chambers through said holes subsequent to the forming of said holes in said blank.

21. Apparatus as claimed in claim 12 wherein said means for advancing said punching tool means operates independently of said means for pressurizing said fluid.

527 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3:5227u9 Dated August 4, 1970 Inventoz-(s) FRANCIS JOSEPH FUCHS, JR.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

' Column 3, lines 10 and 11 (specification page 6,

lines 15 and 16), "lower portion of the hole 19" should have been -lower portion 17 of the hole--;

line MJspecification page 7, line 21),

"34 A" should have been "3 A.

Column 6, line #2 (specification page 15, line 19), "fore" should have been bor*e--.

Column 7, line 22 (specification page 17, line 19), "A" should have been -As.

Column 14, line 6 (specification claim 12, line 11),

"blanks" should have been -blank-.

Signed and sealed this 6th day of July 1971.

(SEAL) Attest:

EDWARD M.EIETCHER,JR. WILLIAM E. SGHUYLER, JR. Attesting Officer Commissioner of Patents 

